66 Grand Teton, Summer Colors 

(Image, June 1998, © 2005 M. Childers)

Get about 6,000 feet over Jenny Lake, and it is possible to have a conversation with one of America’s greatest mountain icons. If you are inclined to pay attention, this one will tell of phenomenal fault-block tilting which, while raising the western rock layers well over their present 13,770 foot elevation, dropped the identical rock layers on the east side of the fault about 7,000 feet beneath the present valley floor.  That is a shift of nearly 21,000 feet.

Part of what is now the floor of Jackson Hole Valley formed from the great volume of eroded rock ground up by glaciers and washed down into the void creating deep canyons in the elevated western side of the fault. The rest comes from erosion of the upper layers of the tilted eastern plate. The eastern slopes of the Teton Mountains are far more precipitous than their western slopes. This same fault-block tilting scenario can be seen in every significant mountain range from the Wasatch Range, in Utah, to the Sierra Nevada Range in California.